The present invention generally relates to controlling transducer movement and, more particularly, to controlling transducer movement responsive to a position error signal.
Disk drives are digital data storage devices which can enable users of computer systems to store and retrieve large amounts of data in a fast and efficient manner. A typical disk drive includes a plurality of magnetic recording disks which are mounted to a rotatable hub of a spindle motor and rotated at a high speed. An array of read/write heads is disposed adjacent surfaces of the disks to transfer data between the disks and a host computer. The heads can be radially positioned over the disks by a rotary actuator and a closed loop servo system, and can fly proximate the surfaces of the disks upon air bearings.
A plurality of nominally concentric tracks can be defined on each disk surface. A preamp and driver circuit generates write currents that are used by the head to selectively magnetize areas of the tracks during a data write operation and amplifies read signals detected by the head during a data read operation. A read/write channel and interface circuit are connected to the preamp and driver circuit to transfer the data between the disks and the host computer.
The servo system can operate in two primary modes: seeking and track following. During a seek, a selected head is moved from an initial track to a target track on the corresponding disk surface. The servo system applies a current command signal to an actuator coil to accelerate the head toward the target track. During the seek, the servo system can measure the location of the head as it moves across the disk based on servo data that is recorded on the disk, and can adjust the current command signal in response to the location measurements. As the head approaches the target track, the servo system decelerates the head to bring it to rest over the target track. Thereafter, the servo system enters the track following mode wherein the head is maintained over the center of the target track while data is written/read.
Vibration of the disk drive can cause the head to have an across-track vibration, which can affect the ability of the servo system to maintain the head on a track during a track following operation. The servo system can be configured to attempt to compensate for a worst-case amount of vibration, within design constraints, that the head may experience while in a track following operation on various tracks across the disk. However, optimizing the servo system for worst-case vibration conditions may provide less than optimal performance (e.g., less input/output of data throughput than otherwise possible) in non-vibration conditions.